Monoclinic titanium dioxide is disclosed in R. Marchand, L. Brohan, M. Tournoux, Material Research Bulletin 15, 1129 (1980). Further, JP-A 2008-34368 (KOKAI) discloses a lithium ion secondary battery using titanium oxide TiO2 having a bronze type structure. JP-A 2008-117625 (KOKAI) discloses a lithium secondary battery using titanium dioxide having a crystal structure of bronze titanate type of which the highest intensity peak is a peak of a (110) plane.
WO2009/028553 A1 discloses a titanium oxide compound of which the highest intensity peak is a peak of a (003) plane, and a half-width (2θ) of the highest intensity peak is 0.4 degree. Therefore, a reversible charge-discharge capacity is lowered.
A battery capacity of each of JP-A 2008-34368 (KOKAI), JP-A 2008-117625 (KOKAI) and WO2009/028553 A1 is considerably lower than about 330 mAh/g which is a theoretical capacity in the case of using monoclinic titanium dioxide for an active material. Further, a practical capacity of spinel type lithium titanate is 170 mAh/g, and, as compared to the spinel type lithium titanate, it is difficult to greatly improve the capacity by using the titanium dioxide described in JP-A 2008-34368 (KOKAI) and JP-A 2008-117625 (KOKAI), and WO2009/028553 A1 as the active material.